An image display surface of an image display device, such as a cathode-ray tube (CRT) display device, a liquid crystal display (LCD), a plasma display (PDP), an electroluminescence display (ELD), and a field emission display (FED), is required to reduce reflection with the light irradiated from the external light source and improve visibility thereof. In order to fulfill the requirement, typically, reflection of the image display surface of an image display device is reduced and visibility thereof is improved, by employing an optical layered body in which an antireflection layer is formed on a light-transmitting substrate.
As the optical layered body having an antireflection layer, there is conventionally known a structure in which a low refractive index layer having a refractive index lower than that of a light-transmitting substrate is provided on the outermost surface.
The low refractive index layer is required to have a low refractive index for the purpose of improving antireflection properties of the optical layered body, to have high hardness for damage prevention because the low refractive index layer is provided on the outermost surface, and to have excellent optical properties such as transparency.
As an optical layered body in which a low refractive index layer is formed on the outermost surface, Patent Document 1, for example, discloses an optical layered body that has a low refractive index layer having a structure that contains hollow silica fine particles thereinside by using a coating liquid containing hollow silica fine particles, a binder resin such as acrylate, and the like.
The display quality required of an image display device, however, has been very high in recent years, and a higher level of antireflection properties of an optical layered body has also been increasingly demanded.
However, the optical layered body in which the conventional low refractive index layer including hollow silica fine particles is provided does not have sufficient antireflection properties and does not satisfy the demand for a high display quality in recent years.
On the other hand, as a method for further reducing a refractive index of a low refractive index layer, Patent Document 2, for example, discloses a method for blending a fluorine atom-containing polymer or monomer in a binder of the low refractive index layer. Since the fluorine atom-containing polymer or monomer is a material with a low refractive index, it is possible to reduce a refractive index of the low refractive index layer containing these in comparison with the conventional low refractive index layer including hollow silica fine particles.
However, when the conventional low refractive index layer containing a fluorine atom-containing polymer or monomer contains these compounds to such an extent that the refractive index is sufficiently reduced, problematically, the hardness of the low refractive index layer may be insufficient, cissing may arise upon applying the composition at the time of forming the low refractive index layer, and a low refractive index layer having an even surface may not be obtained.
Accordingly, there has been required an optical layered body having sufficient hardness and an even surface, including a low refractive index layer having a lower refractive index, and having high antireflection properties.    Patent Document 1: JP-A 2003-292831    Patent Document 2: JP-A 2001-100004